JPS62111093A - Lock-bit with abrasion-resistant insert - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is directed to polycrystalline diamond (P) for perforating deposited layers.
The present invention relates to a locking bit for drilling oil wells, etc., having an insert tipped with a CD.

BACKGROUND OF THE INVENTION Heavy duty rock bits are used in drilling wells into geological formations for oil, gas, geothermal swaths, and the like. This type of bit has a body connected to a drill string and typically three
and a plurality of hollow cutter cones.

The cutter cone has a tjAv integral with the body at its lower end.
J11 - supported on the terminal or bottle. In use, as the cones contact the bottom of the borehole being drilled, the drill string and bit body are rotated within the borehole, with each cone being rotated over its respective borehole. When the lock bit is used on hard layers, high pressures and temperatures are encountered. The total usage IP life of a lock bit in such a harsh environment is approximately 5000 to
, ooort deep and about 6-1/2 to 12-1
20 to 20011 in diameter dimensions of /4 in.
It is 5 minutes. Typically the service life is about 65 to 150 hours.

As the bore hole is drilled, the locking bit becomes worn or damaged, requiring the drill string to be pulled out to replace the bit. The time required to change bits is a significant cost in the drilling operation. This 11.1 interval will occupy 41 parts of the total time to complete the wall, especially as the depth of the 11 houses increases. Therefore, it is clearly desirable to maximize the R life of the drill bit in deposition a3. Extended drilling time minimizes the loss of 10 minutes in time spent "reciprocating" the drill spool to change bits.

Replacement of the drill bit may be necessary for a variety of reasons, including wear or damage to the structure contacting the deposit. The main reason for replacing drill bits and locking bits is damage to the bearings that support the roller cone due to excessive friction, lubricant depletion, etc. There are other non-primary causes for Rock Bit's broken IQ in the formation of the gods. Efforts have continued to improve the functionality and extend the life of these components of locking bits that would otherwise require replacement. Continuous improvements have been made to bearings, but few major improvements have been made to the cutting structure of lock pits.

When the lock pit 1- drills a bore hole, it is important to maintain the diameter or usage of the bore hole at the desired value.

The outermost row of inlets in each cone of the lock pit is known as the gauge row.

This row of inners experiences the greatest friction because it travels the outermost part over the bottom of the hole, and the gauge row inserts experience the greatest friction as the cone rotates on the drill bit body. , there is also a tendency to scrape the side walls of the hole.

As the gauge row insert wears, the diameter of the bore hole being drilled decreases below the original size of the lock bit.

As the bit wears out and is removed, the bottom of the hole typically decreases in size. When the next bit is driven into the hole, it is therefore necessary to widen the bottom of the hole to achieve the full desired size. This actually costs a lot of time (), but
This causes wear of the gauge row insert, which again results in an undersized hole as the second bit wears away. Additionally, as the bit widens the hole, a side load is applied to the cone, causing the bit to pin and providing a high side load to the bearing, which causes premature failure of the bearing.

The penetration rate of the rock bit into the rock debris being drilled is an important parameter of drilling. Obviously, it is desirable to maintain a high rate of drilling, since this reduces the time required to drill a well, which is very expensive due to the fixed costs involved in drilling. As the inner in the cone wears away and no longer protrudes from the cone surface to the same extent as when drilling began, the rate of penetration decreases. The wear insert has an increased radius of curvature and increased lamination contact area. Penetration therefore requires significant force, which results in bearing failure and gauge row insert failure. The drilling speed is continuously observed by the operator, and the bit is replaced when the penetration speed is below an acceptable level and the inlet is worn.

It is therefore important to maximize the wear resistance of the locking bit insert to maintain as high a penetration rate as practicable. In particular, it is important to minimize wear on the gauge row insert and maximize the quality of the perfectly dimensioned holes.

The IT wear resistance of conventional inserts of cemented carbide tungsten carbide is enhanced by increasing the proportion of tungsten carbide and decreasing the proportion of cobalt in J3 in the composite.

This increases the hardness and wear resistance of the cemented tungsten carbide, but reduces its toughness, making the inner more susceptible to fracture than Inser 1-, which has a higher cobalt content. In the illustrated embodiment, the insert used in the locking bit has a Koval 1-containing suspension of approximately 6 to 16 small ω.
%.

Another factor that affects wear resistance and toughness is the size of the tungsten carbide phase particles. Exemplary particle sizes in the insert are 3 to 7 microns. This particle size is the average particle size of the mixed powder including larger and smaller particles.

For example, if the average particle size is 5 microns, there will be particles as large as 7 or 8 microns along with particles of smaller sizes. Toughness generally increases with larger particle size, as does wear resistance. A typical grade of cemented carbide tungsten carbide for rock bit inserts has an average tungsten carbide particle size of about 6 microns and contains about 10-14% cobalt.

The toughness of the inlet is important in rock bits because it is subjected to lj m loads as the cone rotates, as well as wear due to rubbing against the insert I-skin layer. Fracture of the insert becomes an important problem because the fragments of the fractured insert cause other inserts to U 113 without only reducing the drilling action. It is therefore desirable to provide an inner inert that is tough to resist fracture and hard to resist wear.

SUMMARY OF THE INVENTION According to the invention, therefore, the bit has at one end a means for connecting the bit to the drill string, and at the other end a means for connecting the bit to the drill string for rotation about an axis intersecting the axis of the drill bit. A locking bit with a steel body is provided having means for supporting a roller cone. Each roller cone, supported by the body for rotation over the bottom of the borehole being drilled, includes a plurality of inlets for breaking up rock at the bottom of the borehole. At least a portion of these inserts consist of a cemented carbide tungsten carbide body having a grip length that seats within the cone and a Tokyo end portion that projects from the surface of the cone. A layer containing a polycrystalline die V'U:nd is provided on the converging end of the carbide body with a transition layer between the polycrystalline diamond crystal layer and the bide body. The transition layer consists of a composite material including diamond crystals and pre-hardened tungsten carbide particles.

Example 1 The exemplary locking bit consists of a steel body 10 having three cutter cones 11 supported at the lower end. Oil L
Lock onto the drill string to drill [etc.
A screw bin 12 is provided at the upper end of the body for assembling the bit. A plurality of tungsten carbide inserts 13 are provided on the surface of the cutter cone to contact the rock debris being drilled.

FIG. 2 is a longitudinal cross-sectional view of the locking bit extending radially from the rotation @ 14 of the locking bit through one of the three legs on which the cutter cone 11 is supported. Each leg includes a sheeple bin 16 extending downwardly and radially inwardly of the lock bit body. The journal bin includes a cylindrical bearing surface with a hard metal insert 11 on its lower portion. Hard metal inserts are typically cobalt- or iron-based alloys welded in place within the grooves of the journal legs and are substantially stronger than the steel forming the journal bin and lock bit body. It has great hardness. An opening 18 corresponding to the insert 11 is provided in the upper part of the journal bin. For example, the groove above is 6
The hard gold 11117 extends to the remaining 40%. The journal bin also has a cylindrical nose 19 at its lower end.

Each cutter cone 11 is in the form of a hollow, generally conical steel body with a tungsten carbide insert 13 embedded into a hole in its outer surface.

The outer rows 20 of inserts on each cone are referred to as gauge rows because these inserts drill the bore hole size or diameter. The tungsten carbide insert provides a drilling action in engaging and fracturing the basement layer at the bottom of the bore hole being drilled as the lock bit is rotated. The cavity in the cone contains a cylindrical bearing surface containing an aluminum-copper inlet 21 housed in a groove of the steel cone or as a floating insert 1- in the groove of the cone.

The aluminum-copper insert 21 in the cone engages the hard metal insert 17 on the leg and provides the main bearing surface for the cone of the bit body 1-. Nose
A box 22 exists between the end of the cavity in the cone and the nose 19 to support the primary thrust load of the cone on the journal bin. Putushi 123 surrounds the nose,
Provides additional bearing surface between the cone and journal bin. .

A plurality of bearing balls 24 are sealed within complementary ball races within the cone and journal bins. The balls are placed in a ball passageway 2 extending through the journal bin between the bearing race and the outside of the pin 1-.
inserted through 6. The cone is first mounted on the V-bin and then the bearing balls 24 are inserted through the ball passages. The ball supports any thrust loads that attempt to dislodge the cone from the journal bin, thus retaining the cone on the journal bin. The balls are held in the J:relay by a ball holder t27 which is inserted through the ball passage 26 after they are in place. A plug 28 is then welded into the end of the ball passage to hold the ball retainer in place.

The bearing surface between the journal bin and cone is
It is lubricated by grease filling the various passageways and grease reservoirs as well as areas adjacent to the bearing surfaces. The grease reservoir is a cavity 2 in the lock bit body connected to the ball passage 2G by a lubricant passage 31.
Consists of 9. The grease also fills a portion of the ball passageway adjacent to the ball retainer, the open groove 18 on the upper side of the distal pin, and the diagonally extending passageway 32 therebetween.

The grease is retained within the bearing structure by a resilient seal in the form of an O-ring 33 between the cone and the internal bottle.

Pressure compensation I nub assembly is greased and heated.
contained within. This subassembly has an opening 36 at the inner end.
It consists of a metal cap 34 with a . A flexible rubber bellows 37 extends from its outer end into the gap. The bellows is held in place by a cap 38 that opens a vent passageway 39 through it. The pressure compensating fit nub assembly is retained within the grease reservoir by snap ring 41.

The bellows has a boss 42 at its inner end which can be seated against the gear 38 at one end of the bellows displacement for sealing the vent passageway 39. The end of the bellows can also seat against the cap 34 at the other end of its stroke, thus sealing the frontage 36.

In the practice of the present invention, at least a portion of the cutting M4 construction of the lock bit is comprised of a tungsten carbide inlet tipped with polycrystalline diamond. An exemplary insert is shown in longitudinal section in FIG. The insert has a cylindrical grip 46 extending along the main portion of the inner. At one end there is a focusing portion 41 which may take on any of a variety of shapes depending on the desired cutting structure. The focusing portion is referred to as a parabolic shape or essentially a cone with a rounded end. This can be chisel-shaped, like a cone, with converging flat cuts and rounded ends on both sides. The focusing portion can be hemispherical or various other shapes known in the art.

The insert is potted or brazed into the roller cone. Each cone has a plurality of flat bottom holes in a circumferential row of its outer surface. The exemplary hole has a diameter approximately 0.13 mm smaller than the diameter of the grip 46 of the exemplary insert. The insert is driven into the hole in the steel cone with a force of several thousand bonds.

The embedded mounting of the insert within the cone holds the insert 1~ tightly in place and prevents it from becoming dislodged during drilling.

The focusing portion of the insert 1- shown in FIG. 3 includes an outer layer 48 for engaging rock when the insert is used in a rock bit, an inner layer 49 between the outer layers, and a main carbide tungsten layer of the insert. and a carbide body.The outer layer of the exemplary embodiment is 125μ thick polycrystalline diamond (
PCD). The inner layer has a thickness of 380 microns and consists of a composite 44 Fl of polycrystalline diamond and pre-tungsten carbide h-bite as disclosed in US Pat. No. 4,525,178.

As used within this Specification, the term polycrystalline diamond refers to the application of sufficiently high pressures and temperatures to individual die V[nd crystals, in accordance with its abbreviation m rPcDJ, to cause grain bonding between adjacent diamond crystals. Refers to materials manufactured by applying pressure.

An exemplary minimum temperature is about 1300°C and an exemplary minimum pressure is about 35 kilobar. The minimum sufficient temperature and pressure in a given embodiment depends on the following parameters, such as the presence of a catalyst for diamond crystals, such as Vapal.

Typically, the catalyst/bonding agent described above is used to ensure grain bonding at selected times, temperatures and pressures of the process. As used herein, PCD remains]
Refers to polycrystalline diamond containing PAL (-. Often P
CD is technically referred to as "sintered Dyn Send."

In the illustrated embodiment, the outer layer of the PCD is comprised of a mixture of diamond crystals and cobalt powder, totaling 13% cobalt or 6% by volume. Desirably the catalytic metal is present in an amount of 1 to 10% by volume. Approximately 65% of diamond crystals are between 4 and 8 microns. The other 35% of diamond crystals are between 1/2 and 1 micron. The diamond crystals can be either natural diamonds or synthetic diamonds produced in a high temperature, high pressure process.

The diamond crystal can be cut to a size of about 1 μm or more. Preferably they extend to about 20 microns. Preferably a mix of dimensions is used for dense packing. Cobalt content d is 1 to 15% by volume and 1"
The content is preferably 10% by volume or less. Other catalysts such as iron or niracle may also be used in some embodiments.

The raw material for making the PCD layer is desirably milled for a sufficient period of time so that the die grains are completely covered with cobalt. The die V is lined with tungsten carbide and blackened in a ball mill using one tungsten carbide ball.
[This is desirable in order to prevent contamination of the battery.] If desired, a
A grinding or planetary mill can be used. The milling operation described above must be of sufficient energy to ``slather'' the cobalt, but must be such as to prevent crushing of the diamond particles. A ball milling operation of -day or 2 days is appropriate. .

When the forbidden material is subjected to high temperatures and sufficient pressures such that the diamond is thermodynamically stable, grain bonding between adjacent diamonds occurs and a single body of polycrystalline diamond is formed.

The intermediate composite layer is formed from a mixture of diamond crystals, cobalt and pre-hardened tungsten carbide particles. Pre-hardened tungsten carbide is made by mixing tungsten carbide powder and cobalt powder in a ball mill or the like. The mixed powder is compacted near the melting point of cobalt and sintered. The resulting compacted body is ground to the desired particle size for use in making the inner layer composite material. In the illustrated embodiment, the inner layer composite contains coarse particles of 325 US mesh (approximately 44μ).
law is used.

The pre-hardened tungsten carbide coarse particles have different tungsten carbide particle sizes and shapes and different cobalt contents ω. The cobalt content can be between 5 and 16% by weight, and the Kungesten carbide particles are preferably between 4 and 15 microns. In the illustrated example, the particle size is 6μ and the cobalt content is 14% by weight.
It is.

In an exemplary embodiment, the inner layer between the layer of polycrystalline diamond and the cemented carbide tungsten carbide U body comprises 40% by volume of the above diamond powder (including 6% by volume cobalt) and 6% by volume of tungsten carbide. Made from a mixture with coarse particles.

Additional cobalt can be included if desired, depending on the cobalt content of the carbide tungsten carbide.

When making composite layer I+l, the desired powders are thoroughly mixed. The diamond crystals and cobalt powder are blackened together in a ball mill as described above. After the first abrasive tungsten carbide phase particles are added, with or without additional cobalt, the mixture is thoroughly combined and combined. is even more important. For example, the powder is milled in a ball mill to add tungsten carbide coarse particles to the die V-[Nand and Kobal]. Milled in a ball mill.
The working time in the mill is 48 hours.

The mixed powder for making the layer on the insert 1 is sintered and bonded to the insert blank 51 of the lock pit 1 in an assembly of the type shown in FIG. Although the insert formed in the illustrated embodiment of FIG. 5 has somewhat different layers than the illustrated embodiment of FIG. 3 described above, the manufacturing technique is the same. insert blank 51
is a cylindrical tungsten carbide with a focusing section at one end.
Consists of a carbide body. The focused part is finished in-length.
It has the external shape of t and the thickness of the layer to be formed on it.
It's thin. The assembly is preferably formed as a double walled deep drawn metal knit. Inner cap 52
is present, and inside it is a preformed lock bit.
In 1 form the desired net shape of the end of the note. The inner cap is a zirconium sheet with a thickness of 50 to 125 microns. The outer cap 53 is 250μ thick 700μ thick. A zirconium sheet 54 and a molybdenum sheet 55 close the assembly at the berth. The zirconium 1-nonone thus formed protects the internal JtAR from the effects of nitrogen and oxygen. The molybdenum can protects the zirconium from the 1'' water that is often present during the high pressure, high temperature press cycles used to form lock bit inserts.

The production of the assembly shown in FIG. 5 with the cobalt-containing diamond powder admixture is carried out in the cap and when the blank is axially symmetrical, it is oriented to the same shape as the insert blank.
1t9FJ by pressing with an object and rotating it.
It will be extended to If spring inserts were to be made, the powder would be spread with a generally conical tool. The powder forming the outer layer is first spread, and then the powder forming the inner layer is spread onto the outer layer.

Finally, the insert blank is placed in place and a metal sheet is added to close the top of the assembly. A small amount of paraffin wax is included within the mixed powder to assist in spreading and retaining the powder within the thin layer. Instead, the layers are inserted into the insert "-1-" before the insert becomes the cap.
Can be formed on the edges of the blank. In other embodiments,
Sufficient wax is included in the powder to form a self-supporting "cap" of the mixed powder that is placed on the inner blank or within the cap. After the assembly has been formed by any of the above techniques, it is desirable to press the assembly through a die and swage the cap tightly against its contents.

One or more of the above assemblies then include bells 1 to .
Placed in a conventional high pressure cell for pressing in a press or cubic press. Various known cell shapes are applicable. The exemplary cell has a graphite heater tube insulated from and surrounding the assembly by a salt or pyrophyllite that seals the cell and transmits pressure. The cell containing one or more of the assemblies for forming the lock bit insert is placed in a high pressure belt or cubic press and the diamond is thermodynamically heated at the temperatures involved in the sintering process. A stable and sufficient pressure is supplied. In the exemplary embodiment, a pressure of 50 kilobar is used.

Once the assembly is at high pressure, a current is passed through the graphite heater tube to raise the temperature of the assembly to at least 1300°C, preferably 1350-400°C. When the assembly has reached a sufficiently high temperature for a sufficient period of time, the electrical current is interrupted and the part is rapidly cooled by heat transfer to the water-cooled anvil of the press. . When the eddy current is below 1300°C, preferably below 200°C, the pressure is released and the cell and its contents are removed from the press.
NoF is issued. Metal cans and other adhesive cans are 4
Completed in 1 by nondo-plast or etching
is rapidly removed from the nerat. The grip of the finished insert is a cylindrical-based die 17r of the desired method that fits tightly into the hole in the cone of the lock bit. Naturally, the double metal of diamond crystals and pre-tungsten carbide particles is sintered at high temperatures and pressures and does not form distinct forms that can be easily separated.

Two experimental cock bits of the present invention were tested while drilling wells in moderately difficult to drill formations in western Texas. The geological formations to be drilled included salt, shale, dolostone, mixed sandstone and dolostone, mixed sandstone and anhydrite, and mixed sandstone and dolostone. Each of these bits was 7 in number and the gauge cross-sectional diameter was 7-8 inches. The shape of the insert used is J3 in the same oil field formation.
It had the same shape as the regular insert (Smith Tool F37 type) of the lock pit 1- which was used as a standard.

As described above, polycrystalline diamond was first inserted into the inserts 1 to 1 of the gauge row in each bit. Each cemented carbide tungsten carbide in]1-t blank was made with 6μ tungsten carbide particles and 14,000% cobalt, the inner layer was 380μ thick with 6% cobalt by volume. It was formed from 40% by volume of a die drawn 7 mondo cobalt mixture and 60% by volume of 325 mesh pre-carbide tungsten carbide particles. The outer layer was PCD with a nominal thickness of 125μ. It is believed that there was some unevenness in the formation of the outer layer, and that the skin was about 75 microns thick in that area.

The other inserts in the cutting structure on the lock bit (other than the gauge insert) were regular tungsten carbide inserts made with 6μ tungsten carbide powder and 14% cobalt.

One of the pits was used from 1514 ft to a depth of 4094 ft, or a total of 2580 ft. The bit is 4
Used for 5 hours and 15 minutes, average penetration rate was 57rt/l+
It was r.

During operation, the load on the bit is 15,000 to 50,000
At 0 Bond (G, 800 to 22.700 kg), the bit rotated at a speed of 67 to 11013 RP. The maximum WR of bits is 425, which is slightly below the average for the locations that are punched. The WR for the load on the bit determines the rotational speed divided by the bit gauge diameter.

This run is compared to a typical bit run in seven neighboring wells drilled by the same drilling rig at generally comparable depths. The average run lasts 54 hours, drills 2,848 feet deep, and has a penetration rate of about 53
It was rt/l+r. Therefore, the die A7 seven-end tip in J3 gauge row on each cone, the bit with the insert was operated at above average penetration speed, and the operating history and drilling depth were slightly below average.

The reason why the total drilling depth was slightly lower was due to excessive speed and i
The gauge row insert 1- failed +41 because the bit was operated in a particularly difficult formation of dolostone with veinlets of sandstone at ui heavy. The destruction of Inreet is detected on the ground,
Drilling with the above bit has been completed.

After the insert was destroyed, it was estimated that the hole was 15 to 20 cm smaller than its original size, and it was necessary to enlarge the hole.

In the example comparable hole, the hole goodness that needs to be widened is about 150 rt knots from zero.

The second experimental bit was operated in the hole at a depth of 1si1rt and pulled out at 3687ft, with a total drilling quality of 217
It was 6ft.

Drilling time was 33 hours and average penetration velocity was 66 ft/l+
It was r. The load on the bit is 15,000 to 55,
000 bond (6,800 to 25,000k (1”)
The speed was between 78 and 120 RPM. The maximum WR of the bit was 545 taps, above the average for the drilled holes.

Nine confirmation wells were drilled with the same drilling rig at roughly comparable depths in the same formation at J3, with an average operating h1 of 2680 ft in approximately 47 hours and an average penetration velocity of 57 f.
It was t,/hr.

A second experimental bit was pulled out of the hole at a time when there was no sign of the bit becoming dull, cracked, or worn out in the ground. Inspection of the bit showed that the diamond tip had no appreciable wear on the gauge row insert. A few gauge row-r inserts had a slight loss of the Diamond Send layer. Under these same drilling conditions, normal MUII!1! Tungsten 7J
- Obvious wear was observed on the bite gauge row in 1 note. Wear on the tungsten carbide insert inward from the gauge row than on a normal bit that covers the tungsten carbide insert in the gauge row. seemed to be few. Almost no wear was observed on the saw bite insert of the test piece. J to many bits
3, the inner insert becomes very worn and the penetration rate is greatly reduced. It is believed that the absence of wear on the gauge row insert not only maintains the integrity of the hole dimensions, but also provides protection for the inner tungsten carbide insert from the gauge row. This occurs because without gage row wear, the load on the bit is spread more evenly over the insert, and the other inserts are not overloaded. The wear-resistant gauge row insert provides another benefit by protecting the bearings used to support the cone on the lock pin body. When the bit wears so that it cuts below size, or when enlarging a hole below size, undue stress is created on the cone bearing. This "pinching" of the pitch causes premature bearing failure. Therefore,
A locking bit embodiment with a PCD preloaded gauge row insert and a cemented carbide insert is preferred in practicing the present invention.

Since the diamond tip 1 [fin 1 note] shows negligible wear, the main reason for the breakage is thought to be near loss or destruction of the inner tip 1-. Therefore, it is desirable that the bit be used at higher rotational speeds and lower load capacities than conventional roller cone lock bits. Good circulation is desirable to quickly remove debris and minimize cone wear.

FIG. 4 shows another embodiment of a polycrystalline diamond tipped lock bit insert according to the present invention. This insert has a conventional carbide tungsten carbide blank 57 that includes a cylindrical grip 58 and a converging end on a portion of the inn that protrudes beyond the surface of the cone. The insert is then embedded within the cone. Adjacent to the cemented carbide tungsten carbide blank at the focused end is an inner layer 59 with a thickness of 380μ. The inner layer is covered by an intermediate layer 60 with a thickness of 250μ. On the other hand, it is covered by an outer layer 61 with a thickness of 125μ.

The outer layer 61 is the PCD described above. The intermediate layer is formed of a mixture of 60 vol.% PCD (including 6 vol.% cobalt) and 40 vol.% pre-hardened tungsten carbide. The inner layer is formed of 40% by volume PCD and 60% by volume pre-hardened tungsten carbide. After sintering at a high temperature and forming a layered composite material as described above, due to phase effects, the volume % is slightly different from the proportion in the original mixture.
-Jru. For example, some diamond will dissolve within the cobalt phase, so the volume fraction of diamond within the PCD and composite will decrease slightly.

By having a layer of l) CD on the outer surface of the focusing portion of the inlet, the I! of the insert when used for Wll is improved. ? Wear is negligible. ]) By providing a transition between the CD layer and the cemented carbide substrate, the transition protects the PCD layer in terms of elastic modulus and thermal expansion coefficient. The intermediate layer 60 in the vicinity of the PCD layer has a relatively high proportion of CD and a low proportion of cemented carbide compared to the inner layer 59, and therefore has a single step in the embodiment described above and illustrated in FIG. Instead, two steps provide a transition between the outer layer and the cemented carbide blank.

FIG. 5 shows yet another embodiment of the inlet according to the present invention. In this example, the focusing portion of the inner blank 51 is placed on the right side of the outer layer 63 of polycrystalline diamond.
Ru. This PCD outer layer has an inner layer 64 that covers the gradual transition in properties between the 1i CD layer and the cemented carbide blank.
It is separated from 1 rank by.

This transition layer is adjacent to the PCD outer layer 63 and has a high proportion of P,
cl') (e.g., 80% by volume or more) and a low proportion of cemented carbide tungsten carbide.

Towards the cemented carbide blank, the diamond content of the 11 layer decreases progressively, and the proportion of pre-tungsten carbide increases accordingly. For example, the content of polycrystalline die A7 Lnd adjacent to the blank is 20% by volume, and the content of pre-tungsten carbide is 80% by volume. The gradual transition of the proportion of die N7 sind within the transition layer was explained by the 'AJ Song Dynasty, P CD
Between the outer layer and the carbide tungsten carbide L [body
In its mechanical nature, it provides a very large number of stages.

The transition layer provides a transition in the important properties of the PCD layer and/J-Byte substrate. This compensates for differences in coefficients of thermal expansion and elasticity. It has a sound speed intermediate between that of PCD and carbide, which means that stress waves traveling through the inlet have less stress concentration at the interface. The transition layer of diamond crystals and pre-hardened tungsten carbide particles is very different from a mixture of diamond, cobalt and carbide powders. Pre-tungsten carbide particles act as multiple "small anvils" that provide pressure distribution within the layer, which is always responsible for the pressure distribution in powder mixing that provides good cohesion. it is conceivable that. The pre-tungsten carbide has smaller pores than the powder mixture, improving the flow UJ properties of the j1 force. Furthermore, the dispersion of carbide within the composite is very different from that of the composite, similar to the use of steel to strengthen bars in concrete compared to powder steel. Significantly different properties can be attributed to differences in dispersion.

It will be obvious that various improvements and modifications can be made in the locking bit according to the invention. 3 cone type lock
An example of a bit is J3 or above with the usual support of a cone.
have been described and exemplified. Dai V Mondo A.1
[A two-cone lock bit or a variety of other lock bits can also be used with the No. 1 lock bit. The PCD tip insert 1- can be used not only for gauge inserts, but also for all types of cutting of lock bits.

Furthermore, changes to the inleat itself will also be obvious. For example, in the example J3 described above, the PCD layer is approximately 125μ
thicker layers may be used if desired. The PCD layer can be between 75 and 600 microns thick. Surprisingly, however, PCD is so resistant to corrosion by drilled deposits that a layer only 125 microns thick is sufficient for long life lock bits. The thickness of the transition layer is 100 μ to 3 III or more, L
can spell.

Other ratios of PCD to precarbide particles in J3 in the transition layer can be used as described above.

For example, these layers may contain 5 to 95% by volume polycrystalline die\
7-cind and 95 to 5% by volume of pre-tungsten carbide. Depending on the bond content of the cemented carbide tungsten carbide, additional cobal is included in the mixture for good sintering of the transition layer. Other metal carbides such as tantalum carbide or titanium carbide may also be used in the song embodiments.

It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the spirit as set forth in the appended claims.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an exemplary lock bit, FIG. 2 is a longitudinal cross-sectional partial view of the lock bit, and FIG. 3 is a longitudinal direction of an embodiment of an inserter for the lock bit. 4 is a longitudinal sectional view of another embodiment of the F insert; FIG. 5 is a longitudinal sectional view of a subassembly for forming the lock bit insert. 10... [J Hoday 11... Cutter Corn 1
2... Pin with screw 13... Inser 1-16.
...Journal bottle 19...Nose 20...
Outer row of inner inert 46...Grip 47...
・Focusing end portion 48...Outer layer 49...Inner layer 51・
... In-leat blank 52 ... Inner key 53 ... Outer cap 57 ... Insert blank 58 ... Grip 59 ... Inner layer 60.
...Middle layer 61...Outer layer 63...Outer layer 64...
・Inner layer special accommodation applicant Smiths International.

Claims (12)

[Claims] (1) a steel body; a means at one end of the body for connecting a bit to a drill string; and at least one roller cone in the body for rotation about an axis transverse to the axis of the bit. and at least one roller cone supported on the body for rotation over the bottom of the bore hole to be drilled; a plurality of inserts in the cone for use, wherein at least a portion of the inserts are made of carbide having a grip length embedded in the cone and a converging end portion protruding from the cone surface. a tungsten carbide body; a polycrystalline diamond layer on a focused end of the carbide body; and a composite comprising diamond crystals and pre-carbide tungsten carbide particles between the polycrystalline diamond layer and the carbide body. 1. A locking bit having a wear-resistant insert, characterized in that: at least one transition layer consisting of a body; and a wear-resistant insert consisting of: 2. The lock bit of claim 1, wherein said transition layer comprises 40% by volume polycrystalline diamond and 60% by volume pre-hardened tungsten carbide particles. (3) The lock bit according to claim (2), wherein the polycrystalline diamond layer contains 1 to 10% by volume of cobalt. (4) A lock bit according to claim 1, wherein the polycrystalline diamond layer has a thickness of 75 to 600 microns. (5) A lock bit according to claim 4, wherein the transition layer has a thickness of 100 to 600 microns. 6. The lock bit of claim 5, wherein said transition layer comprises 5 to 95 volume percent diamond and 95 to 5 volume percent pre-tungsten carbide. (7) a second transition layer between the first transition layer and the carbide tungsten carbide body, the second transition layer having a lower proportion of diamond crystals and a higher proportion of pre-carbide tungsten than the first transition layer; - The lock bit according to claim (1), which is made of a composite material containing carbide. (8) the transition layer has a relatively high diamond content and a relatively low pre-tungsten carbide content adjacent to the polycrystalline diamond layer and a relatively low diamond content and Claim 1 having a gradual transition layer between a relatively high pre-hardened tungsten carbide content.
Lock bits as described in section. (9) The lock bit according to claim (1), wherein the insert is a gauge row insert of the cone. 10. The lock bit of claim 9, wherein the insert inward from the gauge row insert is made of cemented carbide tungsten carbide without a polycrystalline diamond layer. 11. The lock of claim 1, wherein the insert has a convergent end portion selected from the group consisting of a parabolic shape, a rounded cone, a chisel shape, and a hemispherical shape. ·bit. (12) substantially the entire focusing portion of the insert is comprised of a polycrystalline diamond layer, a diamond layer and a carbide tungsten layer;
A lock bit according to claim 1, having a transition layer of diamond crystals and pre-hardened tungsten carbide between the carbide body.